Does my baby's head look normal?

I posted this pic last week wondering about gender, but now that I have been looking at tons of u/s pics, I'm wondering if my baby's head looks like it's meant to look--most skulls I've seen are white and solid looking, and ours has a darker bit. This was taken at 12w1d.

I posted the pics and the links, because for some reason my pics only show up half of the time. I'm worried that there's some sort of problem with the baby--I didn't see my OB after the u/s, and I don't go back until the 29th.